Researchers from Texas A&M University recently published novel insights about the principles underlying tissue scarring and wound healing in a recent paper entitled “TNF-α–stimulated fibroblasts secrete lumican to promote fibrocyte differentiation”, published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS). The team discovered that two particular proteins involved in scar tissue cell-cell communication act together to promote the aberrant differentiation of functional organ cells into connective tissue. These findings could lead to improved therapies and prevention of fibrotic diseases, such as pulmonary fibrosis.
Fibrosis is characterized by the progressive scar tissue accumulation and inflammation of vital organs – mainly lungs, kidneys, liver and heart – due to deficiencies in the body’s healing processes. As the disease evolves, organ function deteriorates, eventually leading to a complete failure. About 45% of all deaths in the U.S per year are associated to this condition. The principal cause of fibrosis is the uncontrolled transformation of specialized organ and immune cells into non-functional scarring tissue. Researchers believe that this process is associated to communication impairments between fibrocytes and fibroblasts, the main cells of scar tissue.
Searching for cause of fibrocyte-fybrobalst miscommunication, the team analyzed lung tissue of human patients with pulmonary fibrosis for the presence of lumican, a naturally produced blood protein. They found out that lumican levels were higher in patients in advanced disease stages. They then turned into a signaling protein secreted by fibrocytes called tumor necrosis factor alpha (TNF-alpha). During scarring, TNF-alpha stimulates the production of lumican by fibroblasts. Excessive levels of lumican elicit the recruitment of monocytes, an immune cell type that can differentiate into wound-healing fibrocytes. This transformation leads to an additional TNF-alpha secretion, which in turn induces the further production of lumican. This positive feedback loop ultimately leads to an excess of scar tissue in the lungs.
“This research may help explain why fibrosis persists, why it is difficult to treat, and may suggest new methods to treat fibrosis,” said Professor Pilling, a co-author of the paper in a press release. These new findings also suggest that targeting lumican signaling may be a useful therapeutic against fibrosis. Professor Gomer, the supervisor of the work, stated, “Our data suggests that lumican may be one of the unknown signals from fibroblasts to fibrocytes that controls part of a runaway feedback loop that encourages fibrosis. Therefore, lumican-inhibiting drugs may prove useful as possible therapeutic treatments for fibrosis.”
In previous studies, the two researchers found that a liver-produced protein called serum amyloid P (SAP) inhibits the formation of fibrocytes, which are effective in the prevention of fibrotic disease in the lungs and hearts of laboratory animals. It seems that SAP and lumican are competitors in scar-tissue formation. According to Professor Gomer, SAP effects seem to overcome those of lumican. “The proof of the pudding is that SAP treatments cause patients to improve, not just stabilize. So to our delight, it looks like SAP is a dominant factor.”
Currently, Promedior Inc, a clinical-trial biotechnology company founded by the two researchers, is developing the promising SAP wound healing technology.